With a storage controller connected to a storage network or a server device connected to a network, it is desirable to continue operating without losing its function, as much as possible, even during a power failure. For example, when it is not possible to receive the supply of AC power from the outside, the function can be maintained for a predetermined time by using a battery or the like.
Nevertheless, the battery required for maintaining the overall device or overall system during a power failure must have a large capacity, and, because such a battery is expensive, large and heavy, it would be unrealistic to equip all systems and devices with such a function unless it is a system that must constantly be in operation even during emergencies. Moreover, the users' needs are often sufficiently satisfied so as long as it is possible to at least resume processing, at the time of power supply recovery, from the state when the power was lost.
PTL 1 discloses reducing the load power by lowering the processing performance according to the duration of power failure, and thereby extending the retention time during an instantaneous power failure. PTL 2 discloses securing the time required for data retention by discontinuing power supply to loads other than circuits required for data retention upon detecting an instantaneous power failure. PTL 3 discloses retaining cache data in a cache memory based on power feeding from a capacitor, and writing the cache data from the cache memory into a non-volatile memory based on power feeding from a battery upon satisfying predetermined conditions. PTL 4 discloses stopping a loading device when the capacity of a secondary battery, which supplies power in place of a main power supply, falls below a first threshold, and activating the loading device when the capacity of the second battery exceeds a second threshold based on regenerated electric power supply.